We have continued our interest in genetic differences in the sense of taste, focusing on the human T1R genes. These genes encode receptors for sweet and umami (savory) substances and are expressed on the surface of taste cells of the tongue. In the past year we have identified a total of 17 coding sequence variants in these three genes. The nature of this variation suggests that these differences specify functional differences in these receptors that may lead to differences in sweet and umami perception between different individuals. We have also made progress in our studies of the genetic causes of stuttering. In the previous year, we identified the location of a gene on chromosome 1 that causes stuttering in one very large family. This family is native to Cameroon, West Africa and consists of 100 individuals, 45 of which stutter as adults. In the past year we discovered two additional families in Cameroon with a similar presentation of stuttering. To confirm and refine our previous findings, we have obtained DNA and speech samples from these two families. One family consists of 73 individuals, 28 of whom are affected, and the other consists of 38 individuals, 16 of whom are affected. In both cases, the occurrence of stuttering is consistent with an autosomal dominant pattern of inheritance with reduced penetrance. Gene-location studies in these two families are currently underway. Our studies are focused on deficits in auditory pitch perception (tune deafness). To do this, we first recruited a cohort of tune-deaf subjects based on screening the general population. By screening a total of 875 medically normal individuals we identified 40 tune deaf subjects, all of whom had normal hearing. We have been administering a battery of auditory tests to these subjects to provide highly detailed information about their hearing, central auditory processing, pure tone pitch discrimination, and auditory memory abilities.